AU2021100688A4 - A Cluster Autonomous Coordination Method Based on GNSS Parallel Baseband Signal - Google Patents
A Cluster Autonomous Coordination Method Based on GNSS Parallel Baseband Signal Download PDFInfo
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- 238000005516 engineering process Methods 0.000 claims abstract description 10
- 238000011084 recovery Methods 0.000 claims abstract description 6
- 238000005259 measurement Methods 0.000 claims description 15
- 230000008569 process Effects 0.000 claims description 9
- 230000008439 repair process Effects 0.000 claims description 9
- 230000003044 adaptive effect Effects 0.000 claims description 6
- 238000004364 calculation method Methods 0.000 claims description 6
- 230000000694 effects Effects 0.000 claims description 6
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- 239000011159 matrix material Substances 0.000 claims description 5
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- 239000000969 carrier Substances 0.000 claims description 3
- 230000002596 correlated effect Effects 0.000 claims description 3
- 230000000875 corresponding effect Effects 0.000 claims description 3
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
- G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
- G01S5/0205—Details
- G01S5/021—Calibration, monitoring or correction
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S1/00—Beacons or beacon systems transmitting signals having a characteristic or characteristics capable of being detected by non-directional receivers and defining directions, positions, or position lines fixed relatively to the beacon transmitters; Receivers co-operating therewith
- G01S1/02—Beacons or beacon systems transmitting signals having a characteristic or characteristics capable of being detected by non-directional receivers and defining directions, positions, or position lines fixed relatively to the beacon transmitters; Receivers co-operating therewith using radio waves
- G01S1/08—Systems for determining direction or position line
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/13—Receivers
- G01S19/23—Testing, monitoring, correcting or calibrating of receiver elements
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
- G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/42—Determining position
- G01S19/48—Determining position by combining or switching between position solutions derived from the satellite radio beacon positioning system and position solutions derived from a further system
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D1/00—Control of position, course, altitude or attitude of land, water, air or space vehicles, e.g. using automatic pilots
- G05D1/02—Control of position or course in two dimensions
- G05D1/021—Control of position or course in two dimensions specially adapted to land vehicles
- G05D1/0212—Control of position or course in two dimensions specially adapted to land vehicles with means for defining a desired trajectory
- G05D1/0221—Control of position or course in two dimensions specially adapted to land vehicles with means for defining a desired trajectory involving a learning process
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
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- Engineering & Computer Science (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Computer Networks & Wireless Communication (AREA)
- Position Fixing By Use Of Radio Waves (AREA)
Abstract
The invention discloses a cluster autonomous coordination method based on GNSS parallel
baseband signal, which comprises the following steps of channel multiplexing, aided tracking,
relative tracking of signals, rapid recovery of carrier phase, self-adaptive adjustment of carrier
phase tracking and anti-multipath of baseband. With the help of channel multiplexing
technology, the invention uses a hardware channel to track 576 independent satellite signals at
the same time, effectively reducing the hardware scale and power consumption. Besides, aided
tracking technology is adopted, in which basic frequency is responsible for the dynamic of
carrier, while other frequencies only track that dynamic residual parts between themselves and
basic frequency. The residual dynamic is usually small, so the bandwidth of aided tracking can
be very narrow to improve observation accuracy and greatly reduce the burden of CPU. Plus,
the relative tracking only tracks relative dynamics of two frequency points, which can achieve
higher tracking accuracy and smaller variance by reducing the bandwidth.
1 /3
The same satellite(
Tracking channel 010
Independent Independent Independent
siglial signal signal<
Tracking channel02 Independent Independent Independent
signal+' signalO signal+'
Independent Independent Independent
nsignal<- signalO signal<
Tracking channel64
Figure 1 A schematic diagram of channel multiplexing of the present invention.
Antenna 1 Antenna 2 Antenna 2 0
Basic Aided Aided
frequency tracking tracking
point F Frequency Frequency
point 1I point I on
Aided Aided Aided
tn ~ 11tacking # ' tracking
Frequency Frequency Frequency
point 2 point 2 point 2
Aided tracking 0 Aided Aided
Frequency a id Frequency ngofth Frequency
point 3 point 3 points
Figure 2 A schematic diagram of aided tracking of the present invention.
Description
1 /3
The same satellite( Tracking channel 010 Independent Independent Independent siglial signal signal<
Tracking channel02 Independent Independent Independent signal+' signalO signal+' Independent Independent Independent nsignal<- signalO signal<
Tracking channel64
Figure 1 A schematic diagram of channel multiplexing of the present invention.
Antenna 1 Antenna 2 Antenna 2 0
Basic Aided Aided frequency tracking tracking point Frequency F Frequency point 1I point I on
Aided Aided Aided tn ~ 11tacking # ' tracking Frequency Frequency Frequency point 2 point 2 point 2 Aided tracking 0 Aided Aided
Frequency a id Frequency ngofth Frequency point 3 point 3 points
Figure 2 A schematic diagram of aided tracking of the present invention.
A Cluster Autonomous Coordination Method Based on GNSS Parallel Baseband
Signal
[01] The invention relates to the technical field of cluster autonomous coordination, in particular to a cluster autonomous coordination method based on GNSS parallel baseband signal.
[02] In the future information battlefield, the UAV (unmanned aerial vehicle) will be more and more widely used to carry out various lethal combat missions. In the prospect of highly information battlefield, UAV combat mode will also change, from single-machine independent combat mode to cluster-to-cluster and cluster-to ground/water target attack mode, that is UAV cluster cooperative operation, which has scale advantages, excellent battlefield survivability and task completion ability. Therefore, it can be used to complete collaborative search, collaborative interference, collaborative attack, collaborative observation / fighting in complex antagonistic environment.
[03] The key problems that need to be solved include large-scale UAV management and control, autonomous formation flight of multiple UAVs, cluster awareness and situation sharing, cluster penetration and attack, cluster combat mission control station, etc., which requires the use of satellite navigation systems. With the successive establishment of various satellite navigation systems, there are more and more satellite signals available in the sky. In recent years, the receivers on the market have the characteristics of multi-system and multi-frequency, which usually can receive more than 200 satellite signals at the same time. However, tracking multi-channel satellite signals will lead to a huge hardware scale and obvious increase in power consumption, which is contrary to the market requirements of low cost, low power consumption and small size. In order to provide enough observations for high-precision algorithms and improve the reliability and output accuracy of the receiver, a special baseband design is needed. In view of this, the invention proposes a cluster autonomous coordination method based on GNSS parallel baseband signal to solve above mentioned problems.
[04] The purpose of the present invention is to propose a cluster autonomous coordination method based on GNSS parallel baseband signal, which uses channel multiplexing technology. It means that the invention can utilize one hardware channel to track 576 independent satellite signals at the same time, thus effectively reducing the hardware scale and power consumption.
[05] To realize aforesaid purpose, following technical scheme is put forward. Specifically, the cluster autonomous coordination method based on GNSS parallel baseband signal comprises the following steps.
[06] Step 1 Channel multiplexing
[07] In the multi-antenna receiver, 64 independent satellite tracking channels are obtained by multiplexing one hardware channel. Each channel simultaneously tracks 9 independent signals from the same satellite, totalling 576 satellite signals. Each tracking channel is flexibly configured as any satellite in the GNSS system and used to track 576 independent satellite signals at the same time, which is realized by FPGA XC7Z20
[08] Step 2 Aided tracking
[09] According to Step 1, a multiplexing channel can track 9 signals from the same satellite at the same time. Accessing the 9 signals to the same channel, wherein, one signal is used as the basic frequency point, and other signals are tracked with the help of the basic frequency signal. The basic frequency point is tracked by adaptive KALMAN filter, which bears the dynamics of carrier. While, other frequency points only track those dynamic residual parts between the frequency point and the basic frequency point due to the aided tracking. Because the residual dynamic is usually small, the bandwidth of aided tracking is narrowed to improve observation accuracy.
[010] Step 3 Relative tracking of signals
[011] The carrier of basic frequency point is used as local oscillator to track other frequency point carriers. The basic frequency point of multi-antenna receiver is responsible for tracking carrier dynamics and satellite dynamics. The relative dynamics between the other two frequency points of main antenna and basic frequency point is 0, while other antennas and main antenna only have relative dynamics caused by carrier rotation. Therefore, each aided frequency point can be relatively tracked by narrow bandwidth to improve the accuracy of relative observation. In relative tracking, ionospheric errors and satellite clock errors contained in corresponding frequency points of different antennas are naturally eliminated in the tracking process, so it is single difference phase observation.
[012] Step 4 Rapid recovery of carrier phase
[013] The maintenance and measurement of carrier phase is the core of baseband design of high-precision receiver. In practical application, the carrier often passes through complex road sections, followed by dramatic change or even disappearance of signal intensity. When the signal weakens, the loop cannot maintain the tracking of carrier phase, but only enter the state of frequency locking tracking or losing lock reacquisition. At this time, the carrier phase is unavailable, and RTK positioning cannot be carried out. However, signal recovery takes several seconds. Under dynamic conditions, the process is longer. As a result, the RTK positioning cannot be recovered until the signal is recovered for a period of time when the vehicle passes through the bridge. In order to improve this situation, an improved wideband phase frequency detector (-167, 16u) is used, which can directly calculate the instantaneous frequency and phase of the carrier in the case of large frequency difference and phase difference, and modify parameters of the loop to make it directly enter the phase-locked tracking state. This process only takes 0.02 seconds to 0.04 seconds.
[014] Step 5 Adaptive adjustment of carrier phase tracking
Traditional loop design does not consider the influence of signal strength
[015] on loop tracking, but usually only sets a uniform parameter bandwidth according to application occasions. In fact, the instantaneous phase measurement accuracy of carrier is directly related to signal strength, so the instantaneous signal-to-noise ratio of signal is also input into the loop to enhance the dynamic adaptability of signal when the signal is strong, and reduce the bandwidth to improve the accuracy when the signal is weak. Third-order KALMAN filter tracking is adopted to adjust the noise matrix according to real-time signal strength, so that accurate carrier phase measurement can be obtained under large dynamic.
[016] Step 6 Baseband anti-multipath
[017] Multipath effect has always been the main unresolved error source in the field of high-precision GNSS measurement. Therefore, anti-multipath technology is necessary, which includes multipath identification and multipath repair. Based on the phase deviation between multipath signal and direct signal, the hardware design of multipath identification is to extract the head and tail of the signal and track the phase difference of the two signals respectively. If the phase difference is not 0, the signal is considered to have multipath. Multipath repair is based on the direct signal. When the direct signal exists in the head of the incident signal, it is taken out as the input of the phase discriminator in hardware. If the signal is strong, the length of the head is shortened to reduce the influence of multipath.
[018] Further improvement lies in that in step 2, a satellite has three frequency points BI, B2 and B3, and nine signals are formed by three antennas, which are correlated due to their same signal source.
[019] Preferably, in step 2, aided tracking is used to reduce the burden on CPU, and its calculation amount is only equivalent to the calculation amount of tracking two independent frequency points, instead of nine.
[020] Preferably, in step 3, different from single difference of ordinary receiver, the loop bandwidth cannot be narrow due to the limitation of carrier dynamics and satellite dynamics, while the relative tracking only tracks the relative dynamics of two frequency points, so that higher tracking accuracy can be obtained by reducing the bandwidth, and the variance is small.
[021] Preferably, in step 4, when the signal is restored, the loop goes through the stages of frequency locking, frequency difference reduction, phase locking, phase difference reduction.
[022] Preferably, in step 4, the common receiver uses a two-quadrant (-R/2, R/2) or four-quadrant (-R, R) phase discriminator, with narrow phase detection range.
[023] Preferably, in step 6, the multipath repair method is related to signal strength, that is, the stronger the signal, the better the anti-multipath effect.
[024] The method has following beneficial effects.
[025] With the help of channel multiplexing technology, the invention uses one hardware channel to track 576 independent satellite signals at the same time, effectively reducing the hardware scale and power consumption. Besides, aided tracking technology is adopted, in which basic frequency is responsible for the dynamic of carrier, while other frequencies only track that dynamic residual parts between themselves and basic frequency. The residual dynamic is usually small, so the bandwidth of aided tracking can be very narrow to improve observation accuracy and greatly reduces the burden of CPU. Plus, the relative tracking only tracks relative dynamics of two frequency points, which can achieve higher tracking accuracy and smaller variance by reducing the bandwidth. Moreover, the improved broadband phase discriminator can directly calculate the instantaneous frequency and phase of the carrier under the condition of large frequency difference and phase difference, and modify parameters of the loop to make the loop directly enter the phase-locked tracking state, which is more efficient. With the third-order KALMAN filter tracking, the noise matrix can be adjusted according to the real-time signal strength, which can get better carrier phase measurement value in large dynamic situation, so it is convenient to apply in large dynamic situation.
[026] Figure 1 is a schematic diagram of channel multiplexing of the present invention.
[027] Figure 2 is a schematic diagram of aided tracking of the present invention.
[028] Figure 3 is an aided tracking implementation diagram of the present invention.
[029] Figure 4 is a graph showing the relationship between signal strength and instantaneous phase measurement accuracy of the present invention.
[030] Figure 5 is a schematic diagram of KALMAN filter tracking of the loop in the present invention.
[031] In order to deepen the understanding of the present invention, the present invention will be further described in detail with examples below. This embodiment is only used to explain the present invention and does not constitute a limitation on the protection scope of the present invention.
[032] As shown in Figs. 1, 2, 3, 4 and 5, this embodiment provides a cluster autonomous coordination method based on GNSS parallel baseband signal, which comprises the following steps.
[033] Step 1 Channel multiplexing
[034] In the multi-antenna receiver, 64 independent satellite tracking channels are obtained by multiplexing one hardware channel. Each channel simultaneously tracks nine independent signals from the same satellite, totalling 576 satellite signals. Each tracking channel is flexibly configured as any satellite in the GNSS system and used to track 576 independent satellite signals at the same time, which is realized by FPGA XC7Z020.
[035] Step 2 Aided tracking
[036] According to Step 1, a multiplexing channel can track nine signals from the same satellite at the same time. A satellite has three frequency points BI, B2 and B3, and nine signals are formed by three antennas, which are correlated due to their same signal source. Accessing the 9 signals to the same channel, wherein, one signal is used as the basic frequency point, and other signals are tracked with the help of the basic frequency signal. The basic frequency point is tracked by adaptive KALMAN filter, which bears the dynamics of carrier. While, other frequency points only track those dynamic residual parts between the frequency point and the basic frequency point due to the aided tracking. Because the residual dynamic is usually small, the bandwidth of aided tracking is narrowed to improve observation accuracy. Preferably, aided tracking is used to reduce the burden on CPU, and its calculation amount is only equivalent to the calculation amount of tracking two independent frequency points, instead of nine.
[037] Step 3 Relative tracking of signals
[038] The carrier of basic frequency point is used as local oscillator to track other frequency point carriers. The basic frequency point of multi-antenna receiver is responsible for tracking carrier dynamics and satellite dynamics. The relative dynamics between the other two frequency points of main antenna and basic frequency point is 0, while other antennas and main antenna only have relative dynamics caused by carrier rotation. Therefore, each aided frequency point can be relatively tracked by narrow bandwidth to improve the accuracy of relative observation. In relative tracking, ionospheric errors and satellite clock errors contained in corresponding frequency points of different antennas are naturally eliminated in the tracking process, so it is single difference phase observation. Different from single difference of ordinary receiver, the loop bandwidth cannot be narrowed due to the limitation of carrier dynamics and satellite dynamics, while the relative tracking only tracks the relative dynamics of two frequency points, so that higher tracking accuracy can be obtained by reducing the bandwidth, and the variance is small.
[039] Step 4 Rapid recovery of carrier phase
[040] The maintenance and measurement of carrier phase is the core of baseband design of high-precision receiver. In practical application, the carrier often passes through complex road sections, followed by dramatic change or even disappearance of signal intensity. When the signal weakens, the loop cannot maintain the tracking of carrier phase, but only enter the state of frequency locking tracking or losing lock reacquisition. At this time, the carrier phase is unavailable, and RTK positioning cannot be carried out. When the signal is restored, the loop goes through the stages of frequency locking, frequency difference reduction, phase locking, phase difference reduction, taking several seconds. Under dynamic conditions, the process is longer. As a result, the RTK positioning cannot be recovered until the signal is recovered for a period of time when the vehicle passes through the bridge. The ordinary receiver uses a two-quadrant (-n/2, u/2) or four-quadrant (-n, u) phase discriminator, with narrow phase detection range. In order to improve this situation, an improved wideband phase frequency detector (-16R, 16R) is used, which can directly calculate the instantaneous frequency and phase of the carrier in the case of large frequency difference and phase difference, and modify parameters of the loop to make it directly enter the phase-locked tracking state. This process only takes 0.02 seconds to 0.04 seconds.
[041] Step 5 Adaptive adjustment of carrier phase tracking
[042] Traditional loop design does not consider the influence of signal strength on loop tracking, but usually only sets a uniform parameter bandwidth according to application occasions. In fact, the instantaneous phase measurement accuracy of carrier is directly related to signal strength, so the instantaneous signal-to-noise ratio of signal is also input into the loop to enhance the dynamic adaptability of signal when the signal is strong, and reduce the bandwidth to improve the accuracy when the signal is weak. Third-order KALMAN filter tracking is adopted to adjust the noise matrix according to real-time signal strength, so that accurate carrier phase measurement can be obtained under large dynamic.
[043] Step 6 Baseband anti-multipath
[044] Multipath effect has always been the main unresolved error source in the field of high-precision GNSS measurement. Therefore, anti-multipath technology is necessary, which includes multipath identification and multipath repair. Based on the phase deviation between multipath signal and direct signal, the hardware design of multipath identification is to extract the head and tail of the signal and track the phase difference of the two signals respectively. If the phase difference is not 0, the signal is considered to have multipath. Multipath repair is based on the direct signal. When the direct signal exists in the head of the incident signal, it is taken out as the input of the phase discriminator in hardware. If the signal is strong, the length of the head is shortened to reduce the influence of multipath. The multipath repair method is related to signal strength, that is, the stronger the signal, the better the anti-multipath effect.
[045] With the help of channel multiplexing technology, the invention uses one hardware channel to track 576 independent satellite signals at the same time, effectively reducing the hardware scale and power consumption. Besides, aided tracking technology is adopted, in which basic frequency is responsible for the dynamic of carrier, while other frequencies only track that dynamic residual parts between themselves and basic frequency. The residual dynamic is usually small, so the bandwidth of aided tracking can be very narrow to improve observation accuracy and greatly reduces the burden of CPU. Plus, the relative tracking only tracks relative dynamics of two frequency points, which can achieve higher tracking accuracy and smaller variance by reducing the bandwidth. Moreover, the improved broadband phase discriminator can directly calculate the instantaneous frequency and phase of the carrier under the condition of large frequency difference and phase difference, and modify parameters of the loop to make the loop directly enter the phase-locked tracking state, which is more efficient. With the third-order KALMAN filter tracking, the noise matrix can be adjusted according to the real-time signal strength, which can get better carrier phase measurement value in large dynamic situation, so it is convenient to apply in large dynamic situation.
[046] Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms, in keeping with the broad principles and the spirit of the invention described herein.
[047] The present invention and the described embodiments specifically include the best method known to the applicant of performing the invention. The present invention and the described preferred embodiments specifically include at least one feature that is industrially applicable
Claims (7)
1. A cluster autonomous coordination method based on GNSS parallel baseband signal, characterized by comprising the following steps:
Step 1 Channel multiplexing
In the multi-antenna receiver, 64 independent satellite tracking channels are obtained by multiplexing one hardware channel. Each channel simultaneously tracks 9 independent signals from the same satellite, totalling 576 satellite signals. Each tracking channel is flexibly configured as any satellite in the GNSS system and used to track 576 independent satellite signals at the same time, which is realized by FPGA XC7Z20
. Step 2 Aided tracking
According to Step 1, a multiplexing channel can track 9 signals from the same satellite at the same time. Accessing the 9 signals to the same channel, wherein, one signal is used as the basic frequency point, and other signals are tracked with the help of the basic frequency signal. The basic frequency point is tracked by adaptive KALMAN filter, which bears the dynamics of carrier. While, other frequency points only track those dynamic residual parts between the frequency point and the basic frequency point due to the aided tracking. Because the residual dynamic is usually small, the bandwidth of aided tracking is narrowed to improve observation accuracy.
Step 3 Relative tracking of signals
The carrier of basic frequency point is used as local oscillator to track other frequency point carriers. The basic frequency point of multi-antenna receiver is responsible for tracking carrier dynamics and satellite dynamics. The relative dynamics between the other two frequency points of main antenna and basic frequency point is 0, while other antennas and main antenna only have relative dynamics caused by carrier rotation. Therefore, each aided frequency point can be relatively tracked by narrow bandwidth to improve the accuracy of relative observation. In relative tracking, ionospheric errors and satellite clock errors contained in corresponding frequency points of different antennas are naturally eliminated in the tracking process, so it is single difference phase observation.
Step 4 Rapid recovery of carrier phase
The maintenance and measurement of carrier phase is the core of baseband design of high-precision receiver. In practical application, the carrier often passes through complex road sections, followed by dramatic change or even disappearance of signal intensity. When the signal weakens, the loop cannot maintain the tracking of carrier phase, but only enter the state of frequency locking tracking or losing lock reacquisition. At this time, the carrier phase is unavailable, and RTK positioning cannot be carried out. However, signal recovery takes several seconds. Under dynamic conditions, the process is longer. As a result, the RTK positioning cannot be recovered until the signal is recovered for a period of time when the vehicle passes through the bridge. In order to improve this situation, an improved wideband phase frequency detector (-167, 16u) is used, which can directly calculate the instantaneous frequency and phase of the carrier in the case of large frequency difference and phase difference, and modify parameters of the loop to make it directly enter the phase-locked tracking state. This process only takes 0.02 seconds to 0.04 seconds.
Step 5 Adaptive adjustment of carrier phase tracking
Traditional loop design does not consider the influence of signal strength on loop tracking, but usually only sets a uniform parameter bandwidth according to application occasions. In fact, the instantaneous phase measurement accuracy of carrier is directly related to signal strength, so the instantaneous signal-to-noise ratio of signal is also input into the loop to enhance the dynamic adaptability of signal when the signal is strong, and reduce the bandwidth to improve the accuracy when the signal is weak. Third-order KALMAN filter tracking is adopted to adjust the noise matrix according to real-time signal strength, so that accurate carrier phase measurement can be obtained under large dynamic.
Step 6 Baseband anti-multipath
Multipath effect has always been the main unresolved error source in the field of high-precision GNSS measurement. Therefore, anti-multipath technology is necessary, which includes multipath identification and multipath repair. Based on the phase deviation between multipath signal and direct signal, the hardware design of multipath identification is to extract the head and tail of the signal and track the phase difference of the two signals respectively. If the phase difference is not 0, the signal is considered to have multipath. Multipath repair is based on the direct signal. When the direct signal exists in the head of the incident signal, it is taken out as the input of the phase discriminator in hardware. If the signal is strong, the length of the head is shortened to reduce the influence of multipath.
2. The cluster autonomous coordination method based on GNSS parallel baseband signal according to Claim 1, characterized in that in step 2, a satellite has three frequency points B1, B2 and B3, and nine signals are formed by three antennas, which are correlated due to their same signal source.
3. The cluster autonomous coordination method based on GNSS parallel baseband signal according to Claim 1, characterized in that, in step 2, aided tracking is used to reduce the burden on CPU, and its calculation amount is only equivalent to the calculation amount of tracking two independent frequency points, instead of nine.
4. The cluster autonomous coordination method based on GNSS parallel baseband signal according to Claim 1, characterized in that in step 3, different from single difference of ordinary receiver, the loop bandwidth cannot be narrow due to the limitation of carrier dynamics and satellite dynamics, while the relative tracking only tracks the relative dynamics of two frequency points, so that higher tracking accuracy can be obtained by reducing the bandwidth, and the variance is small.
5. The cluster autonomous coordination method based on GNSS parallel baseband signal according to Claim 1, characterized in that in step 4, when the signal is restored, the loop goes through the stages of frequency locking, frequency difference reduction, phase locking, phase difference reduction.
6. The cluster autonomous coordination method based on GNSS parallel baseband signal according to Claim 1, characterized in that in step 4, the common receiver uses a two-quadrant (-n/2, 7/2) or four-quadrant (-u, u) phase discriminator, with narrow phase detection range.
7. The cluster autonomous cooperation method based on GNSS signal parallel baseband according to Claim 1, characterized in that in step 6, the multipath repair method is related to signal strength, that is, the stronger the signal, the better the anti multipath effect.
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| CN116470956A (en) * | 2023-06-19 | 2023-07-21 | 成都川美新技术股份有限公司 | Channel tracking method and system for backtracking time-frequency signal in non-guiding mode |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116470956A (en) * | 2023-06-19 | 2023-07-21 | 成都川美新技术股份有限公司 | Channel tracking method and system for backtracking time-frequency signal in non-guiding mode |
| CN116470956B (en) * | 2023-06-19 | 2023-10-13 | 成都川美新技术股份有限公司 | Channel tracking method and system for backtracking time-frequency signal in non-guiding mode |
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